US Secretary of State Rex Tillerson on Friday visited the demilitarized zone, the highly-fortified border between North and South Korea, becoming the most senior US official to visit the area since President Barack Obama in 2012.

Tillerson met with some of the more than 28,000 US troops on the peninsula. South and North Korea are still technically at war after the Korean War ended in 1953 with in an armistice but no peace treaty.

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During his trip, he visited the Joint Security Area, where North and South Korea soldiers stand facing each other and a Military Armistice Commission briefing room straddles the border.

The relatively inexperienced Tillerson has waded into a political minefield in South Korea, where President Park Geun-hye was impeached a week ago and preparations are being made for a snap election on May 9.

Politics

After visiting the DMZ, Tillerson is due to meet acting President Hwang Kyo-ahn and Foreign Minister Yun Byung-se.

Tillerson is expected to seek assurances that South Korea will continue to honor an agreement to deploy the Terminal High Altitude Area Defense (THAAD) system, the first parts of which arrived in South Korea earlier this month.

However, neither Hwang and Yun are expected to be in their current roles after the election; the country is widely expected to swing to the left in the wake of Park's impeachment.

The Democratic United Party's Moon Jae-in, who currently leads in the polls, has been critical of the THAAD agreement and suggested it should be renegotiated, saying Park should have sought the approval of the National Assembly before deployment began.

"It's not urgent," Democratic lawmaker Song Young-gil told CNN. "The more urgent critical thing is how we can prevent (North Korean) nuclear testing, the sixth test."

Tillerson may be more open than his predecessors to seeking a new path on North Korea however. Speaking in Tokyo this week, he said that all the efforts of the past 20 years "have failed."

China will formally present its own proposal to Tillerson on Saturday when he visits the country, a senior Chinese diplomat told CNN Thursday.

Tourists and threats

Over the years, many top US officials have visited the DMZ, which President Bill Clinton described in 1993 as the "scariest place on Earth."

Since then though, the DMZ has become a major tourist attraction, with thousands of visitors every day.

The DMZ is not completely peaceful however. Both sides have used the border as a site to broadcast propaganda via huge loudspeakers into the neighboring country.

Seoul ordered the resumption of such broadcasts after the North's reported hydrogen bomb test in January 2016, which continue to this day.

In the past, Pyongyang has threatened military strikes against the speakers, calling them a "grave military provocation."

Threats have also been made against South Korean activists who regularly float large numbers of balloons across the DMZ carrying anti-regime propaganda and information about the South.